X-ray transmission spectrometer system

ABSTRACT

An x-ray spectrometer system includes an x-ray source, an x-ray optical system, a mount, and an x-ray spectrometer. The x-ray optical system is configured to receive, focus, and spectrally filter x-rays from the x-ray source to form an x-ray beam having a spectrum that is attenuated in an energy range above a predetermined energy and having a focus at a predetermined focal plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

Patent application is a Continuation-in-Part of U.S. patent applicationSer. No. 15/431,786, filed Feb. 14, 2017, which in turn is aContinuation-in-Part of U.S. patent application Ser. No. 15/269,855,filed Sep. 19, 2016 now issued as U.S. Pat. No. 9,570,265, and is also aContinuation-in-Part of U.S. patent application Ser. No. 15/166,274,filed May 27, 2016, all of which are hereby incorporated by reference intheir entirety. Additionally, U.S. patent application Ser. No.15/269,855 is a Continuation-in-Part of U.S. patent application Ser. No.14/544,191, filed Dec. 5, 2014 and now issued as U.S. Pat. No.9,449,781, which is hereby incorporated by reference in its entirety,and which claims the benefit of U.S. Provisional Patent Application Nos.61/912,478, filed on Dec. 5, 2013, 61/912,486, filed on Dec. 5, 2013,61/946,475, filed on Feb. 28, 2014, and 62/008,856, filed on Jun. 6,2014, all of which are incorporated herein by reference in theirentirety. Application Ser. No. 15/269,855 is also a Continuation-in-Partof U.S. patent application Ser. No. 14/636,994, filed Mar. 3, 2015 andnow issued as U.S. Pat. No. 9,448,190, which is hereby incorporated byreference in its entirety, and which in turn claims the benefit of U.S.Provisional Patent Application Nos. 62/008,856, filed Jun. 6, 2014;62/086,132, filed Dec. 1, 2014, and 62/117,062, filed Feb. 17, 2015, allof which are incorporated herein by reference in their entirety.

BACKGROUND

Measurement of the x-ray absorption properties of a material near theionization energy can reveal information about the chemical state of theelements of interest within a sample, revealing information such asoxidation state and coordination number.

X-ray absorption spectroscopy (XAS) measures the fraction of x-raysabsorbed by an object as a function of x-ray energy over a predeterminednarrow energy range. It is often carried out at synchrotron lightsources because of their high brightness and energy tunability.Unfortunately, synchrotron based x-ray absorption spectroscopy systemshave numerous accessibility limitations, such as long wait times toobtain proposal-based access, limited measurement time granted per usergroup, and logistic issues including the need for travel and shipment ofspecial experiment.

Small laboratory-based x-ray absorption spectroscopy systems wouldprovide easy access and full control, however the performance oflaboratory XAS systems has been largely limited by a combination of manyfactors, including low brightness and flux of laboratory x-ray sources,low efficiency of the x-ray optic used, and low diffraction efficiencyof the crystal analyzer associated with the use of high indexreflections required for high energy resolution measurements due to thetypically large x-ray source sizes of laboratory sources. Thoselimitations result in unacceptably long acquisition times (˜tens ofhours) and/or poor energy resolution. As a result, there are fewlaboratory systems in use.

There is a need for a laboratory x-ray absorption spectroscopy systemwith high throughput that circumvents the limitations of priorlaboratory XAS systems.

SUMMARY

The present technology, roughly described, is an x-ray absorptionspectrometer usable with a compact x-ray source to measure x-raytransmission with high throughput, high spatial, and high spectralresolution. In some instances, the spectrometer includes an opticalx-ray optic system which achromatically focuses x-rays emerging from thex-ray source to preserve the brightness of the x-ray source, also servesas a low-pass filter with a predetermined high-energy cut-off for thex-rays. One major advantage of the use of an x-ray optical systemserving as low-pass focusing reflector is that the energy of theelectrons of the x-ray source can be substantially higher than thepredetermined high-energy cut-off, increasing the x-ray productionefficiency to achieve high source brightness. This x-ray optical systemcan provide a point or a line focus that serves as the virtual sourcefor x-rays in a spectrometer comprising of a crystal analyzer.

In some instances, a method for x-ray absorption spectroscopy by anx-ray optical system includes collecting x-rays received from a firstx-ray source through an x-ray optical system. The x-ray optical systemhas low-pass spectral filter properties such that x-rays above a cut-offenergy are reduced. A focused x-ray beam is produced by the x-rayoptical system with a focus at a predetermined focal plane downstream ofthe x-ray optical system. The focused x-ray beam passes through a sampleto be analyzed. The focused x-ray beam acts as a secondary source ofdiverging x-rays located at the focal plane. The diverging x-rays fromthe secondary source are received by an x-ray spectrometer having anx-ray wavelength dispersive element and an analyzer to analyze thespectrum of the dispersed x-rays.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an exemplary x-ray spectrometersystem 200.

FIG. 2 illustrates an x-ray radiation spectrum.

FIG. 3 illustrates a portion of a target comprising three x-raygenerating structures, each having a different x-ray generatingmaterial, as may be used in some embodiments of the invention.

FIG. 4A illustrates a cross section schematic view of an x-ray sourceand an optical system comprising an ellipsoidal optical element as maybe used in some embodiments of the invention.

FIG. 4B illustrates a perspective schematic view of a portion of thex-ray source and optical system of FIG. 4A

FIG. 5A illustrates a cross section schematic view of an x-ray sourceand an optical system comprising a pair of paraboloidal optical elementsas may be used in some embodiments of the invention.

FIG. 5B illustrates a perspective schematic view of a portion of thex-ray source and optical system of FIG. 5A

FIG. 6 illustrates a cross section schematic view of a spectrometersystem using a single crystal analyzer according to the invention.

FIG. 7 illustrates a cross section schematic view of the spectrometerportion of the system illustrated in FIG. 11.

FIG. 8A illustrates a cross section schematic view of the spectrometerportion of a system similar to that illustrated in FIG. 11, but using amosaic crystal.

FIG. 8B illustrates a schematic view of a spectrometer such as thatillustrated in FIG. 13B, additionally arranged to show the relatedRowland Circles.

FIG. 9 illustrates a perspective schematic view of a spectrometer systemas may be used in some embodiments of the invention.

FIG. 10 illustrates a perspective schematic view of a spectrometersystem having multiple options for x-ray source, optical system,aperture, and crystal analyzer position as may be used in someembodiments of the invention.

FIG. 11 illustrates a cross section schematic view of a spectrometersystem using a single crystal analyzer according to the invention.

FIG. 12A presents a portion of the steps of a method for collectingspectroscopy data according to an embodiment of the invention.

FIG. 12B presents the continuation of the steps of the method of FIG.12A for collecting spectroscopy data according to an embodiment of theinvention.

FIG. 12C presents the continuation of the steps of the method of FIGS.12A and 12B for collecting spectroscopy data according to an embodimentof the invention.

DETAILED DESCRIPTION

Instances of the present technology include an x-ray absorptionspectrometer usable with a compact x-ray source (e.g., first source) tomeasure x-ray transmission with high throughput, high spatial, and highspectral resolution. In some instances, the spectrometer includes anx-ray optical system which achromatically focuses x-rays emerging fromthe x-ray source that preserves the brightness of the x-ray source andalso serves as a low-pass filter with a predetermined high-energycut-off for the x-rays. One major advantage of the use of an x-rayoptical system serving as low-pass focusing reflector is that theaccelerating voltage of the electrons of the x-ray source can besubstantially higher than the predetermined high-energy cut-off,increasing the x-ray production efficiency to achieve high sourcebrightness. This optical system can provide a point or a line focus thatserves as the virtual source for x-rays in a spectrometer that includesof a crystal analyzer.

The x-ray optical elements in the train may include paraboloid optics,ellipsoidal optics, polycapillary optics, or various types of Wolteroptics, Kirkpatrick-Baez mirrors or multilayers suitably graded andsystems comprising combinations thereof. The high collection andfocusing efficiency achievable using these optical elements helpsachieve high flux density in tightly focused spots.

In some embodiments, the higher brightness compact x-ray source isachieved in part through the use of novel x-ray targets used ingenerating x-rays from electron beam bombardment. These x-ray targetconfigurations may include a number of microstructures of one or moreselected x-ray generating materials fabricated in close thermal contactwith (such as embedded in or buried in) a substrate with high thermalconductivity, such that the heat is more efficiently drawn out of thex-ray generating material. This in turn allows bombardment of the x-raygenerating material with higher electron density and/or higher energyelectrons, which leads to greater x-ray brightness and greater x-rayflux.

An object to be examined in transmission is placed in the x-ray beam,and an aperture is placed at the point or line of focus to selectivelypass the transmitted x-rays while restricting the widely radiated x-rayfluorescence and any scattered radiation that may exist. The object maybe translated in x- and y-axes to allow a 2-D “map” of the transmissionspectrum to be collected.

The aperture placed at the point or line of focus becomes the “source”(often referred to as the virtual source or second source) for a secondx-ray optical system (the spectrometer) designed to disperse x-raysemerging from the aperture. This second system uses diffractive analyzercrystals to diffract x-rays of different energies onto an arraydetector, aligned so that different pixels of the detector correspond todifferent x-ray energies.

In some embodiments, an additional beam stop may be placed after theaperture to block the directly transmitted beam, but allow x-rayfluorescence emitted by the object to enter the spectrometer and bespectroscopically analyzed.

The present x-ray optical system may have several advantages. One ormore optics of the x-ray optical system can be used as a low pass filterto cut out and/or reduce the energy of at least a portion of the x-raysprovided by an x-ray source to provide a second source for directing ata target. Additionally, the x-ray optical system may allow selection ofone of a plurality of optics. This interchangeability of sources basedon a selected optic provides different spectrums that can be optimizedfor different tasks.

The present x-ray optical system also provides for high spatialresolution. The present system can interrogate a sample and raster scanthe sample at a spatial resolution of 10 microns, for example. Thisdegree of spatial resolution is much stronger than prior systems, whichfor example provide resolution at a millimeter level.

The present x-ray optical system further provides a sample holder ormount that can include multiple samples without requiring a door of thesystem to be opened, and wherein each sample can be positioned at adistance from the source other than at or close to the source. In someinstances, the mount can receive one or more of a plurality of samplesand positions at least one sample in the focused x-ray beam foranalysis. This variable sample positioning is better suited to changesin temperature and/or the environment and therefore provides for moreaccurate analysis of the sample. Further, the sample can bemicro-fluidic, allowing x-rays to flow through samples of a differentmaterial.

1. An Exemplary Spectrometer System.

FIG. 1 illustrates a block diagram of an exemplary x-ray spectrometersystem 200. The spectrometer system 200 of FIG. 1 includes an x-raysource 80, an x-ray optical system 3000 that includes an object 240 tobe examined by x-ray transmission, a spectrometer 3700 includingdetector 290, signal processing electronics 292, and an analysis system295 having a display 298.

The exemplary x-ray source 80 (e.g., first source) includes a vacuumenvironment (typically 10⁻⁶ torr or better) commonly maintained by asealed vacuum chamber 20 or active pumping. Vacuum chamber 20 can bemanufactured with sealed electrical leads 21 and 22 that pass from thenegative and positive terminals of a high voltage source 10 outside thetube to the various elements inside the vacuum chamber 20. The source 80can include mounts 30 which secure the vacuum chamber 20 in a housing50. The housing 50 may include shielding material, such as lead, toprevent x-rays from being radiated by the source 80 in unwanteddirections.

Inside vacuum chamber 20, an electron emitter 11 is coupled through lead21 to the negative terminal of a high voltage source 10, which serves asa cathode and generates a beam of electrons 111, for example by runninga current through a filament. Any number of prior art techniques forelectron beam generation may be used for the embodiments of theinvention disclosed herein. Additional known techniques used forelectron beam generation include heating for thermionic emission,Schottky emission (a combination of heating and field emission),emitters including nanostructures such as carbon nanotubes, and by useof ferroelectric materials.

A target 1100 includes a target substrate 1000 and x-ray generatingstructures 700, which can include one or more x-ray generatingmaterials. Target 1100 is electrically connected to the opposite highvoltage lead 22 via target support 32 to be at ground or a positivevoltage relative to the electron emitter 11, thus serving as an anode.The electrons 111 accelerate towards the target 1100 and collide with itat high energy, with the energy of the electrons determined by themagnitude of the accelerating voltage. The collision of the electrons111 into the target 1100 induces several effects, including theradiation of x-rays 888, some of which exit the vacuum chamber 20 andare transmitted through a window 40 designed to be transparent tox-rays.

In some instances, there can also be an electron control mechanism 70such as an electrostatic lens system or other system of electron optics.Control mechanism 70 can be controlled and coordinated with the electrondose and voltage provided by the electron emitter 11 by a controller10-1 through an additional lead 27. The electron beam 111 may thereforebe scanned, focused, de-focused, or otherwise directed onto target 1100,which can include one or more x-ray generating structures 700 fabricatedto be in close thermal contact with a substrate 1000.

Once x-rays 888 exit the x-ray source 80, a portion of the x-rays arecollected by optical system 3000. Optical system 3000 can include one ormore optical systems 840 having x-ray optical elements with axialsymmetry. The elements of the optical system 840 reflect x-rays atgrazing angles to focus a portion 887 of the x-rays onto an aperturecomponent 270 having one or more apertures 272. The object 240 to beexamined is typically placed in a mount 244 and positioned at the focusor just before the aperture 272. The mount may allow the object 240 tobe translated and/or rotated so that different portions of the object240 are illuminated by the x-ray beams 887, allowing different positionson the object 240 to be illuminated in a systematic scan or from severalangles of incidence, with this motion controlled by a controller 246.X-rays propagating along the axis of the optical system that are notcollected and focused may be blocked by a beam stop 850.

Once the focused portion of the x-rays 887 converge onto the object 240,the transmitted x-rays 888-T that also pass through the aperture 272 arecollected by a spectrometer 3700. The spectrometer 3700 typicallyincludes at least one dispersing x-ray crystal and an x-ray detector290. The detector 290 will typically be an array detector, positioned torecord the intensity of the dispersed x-rays as a function of position.Additional signal processing electronics 292 and analysis system 295correlate the intensity signals to the corresponding x-ray energy. Theanalysis system 295 may additionally include a display 298. The detector290 may also include sensors and electronics that serve as an x-rayspectrometer, analyzing both the number of x-ray fluorescence photonsemerging from the object 240 as well as their energy.

Additional embodiments of x-ray sources have been described in U.S.patent applications “X-RAY SOURCES USING LINEAR ACCUMULATION” (U.S.patent application Ser. No. 14/490,672, filed Sep. 19, 2014 and nowissued as U.S. Pat. No. 9,390,881), “X-RAY SOURCES USING LINEARACCUMULATION” (U.S. patent application Ser. No. 14/999,147, filed Apr.1, 2016, and now issued as U.S. Pat. No. 9,543,109), and “DIVERGINGX-RAY SOURCES USING LINEAR ACCUMULATION” (U.S. patent application Ser.No. 15/166,274 filed May 27, 2016), all of which are hereby incorporatedby reference in their entirety, along with any provisional applicationsto which these patents and co-pending patent applications claim benefit.

Any of the target and/or source designs and configurations disclosed inthe above referenced patents and patent Applications may be consideredfor use as a component in any or all of the methods or systems disclosedherein. Such variations may include active cooling systems havingchannels that carry liquid near or into the target to remove heat,mechanisms to rotate the anode to allow different portions to bebombarded by electrons while other recently bombarded portions cool,systems including multiple electron beams that bombard opposite sides ofa target to increase x-ray brightness through linear accumulation, andsystems that additionally use multiple anodes aligned to create an x-raybeam through linear accumulation from several sources.

The components illustrated in the Figures are exemplary, and the variouselements (microstructures, surface layers, cooling channels, etc.) arenot intended to be limiting. It should also be noted that the x-raysource used for embodiments of the invention may be a microfocus,nanofocus, or rotating anode source using bombardment of a solid anodetarget by electrons, but that the target may also include multiple x-raygenerating materials, and may additionally contain regions in which thex-ray generating materials are molten or liquid. Furthermore, the x-raysource may be any x-ray source designed to use a liquid metal (such as agallium liquid metal jet) as the anode.

2. X-Ray Source Spectrum.

FIG. 2 illustrates an x-ray radiation spectrum for 100 keV electronexcitation with a tungsten (W) target. The broad spectrum x-rayradiation continuum 388, commonly called bremsstrahlung, is larger atlower energy and decreases at energies approaching the excitation energyof 100 keV. Characteristic lines 988 for tungsten are also illustrated.

This exemplary spectrum is modified for use in a spectroscopy system tolimit the x-ray bandwidth. As discussed with respect to FIG. 1, thex-ray source 80 will typically have a window 40. This window 40 mayattenuate low energy x-rays. Shown in FIG. 2 is a modified energyspectrum 488 for the x-rays that results from using an SiO₂ window 100microns thick. Some laboratory sources either come with a Be window(normally 200-300 um thick) or with a diamond window (normally ˜200-300um thick), which also doubles up as a target substrate in thetransmission source type. The system may additionally include a filter,such as a sheet or layer of aluminum, placed near the source or on thewindow to further attenuate low energy x-rays.

For a spectrometer, broad-spectrum x-rays can be used, and in someinstances can be preferred, and characteristic lines 988 may make thetask of interpreting the resulting spectra more difficult. It istherefore often advantageous to have the optical system collecting andfocusing the x-rays designed to serve as a low-pass filter, severelyattenuating any characteristic lines that may be generated and highenergy bremsstrahlung background.

The optical system can include one or more x-ray optical elements inwhich the x-rays illuminates the inner surface of the element at anear-grazing angle (e.g. at angles of a few degrees or smaller). Theoptics may be coated with a particularly selected material, such thatthe critical angle of reflection can be exceeded for the higher energyx-rays, and the higher energy x-rays may not be efficiently reflected bythe optical surface. As such, the x-ray optical system can have low-passspectral filter properties such that x-rays above a cut-off energy arereduced as they pass through the optic system. X-rays below the cut-offenergy may be focused to a predetermined focal plane.

Also in FIG. 2, a modified energy spectrum 588 that results from using asilver (Ag) coating on the interior of a capillary with a grazing angleof incidence of 3.5 mrad (0.2005 degrees), as calculated using thewebsite

-   -   henke.lbl.gov/optical_constants/layer2.html.        X-ray energies above 17.4 keV are significantly attenuated,        providing 17.4 keV as a “high-energy cutoff” for reflection in        this system. This cuts out the strong tungsten characteristic        lines at higher energy. When combined with the “high pass”        filter provided by the window, the “low-pass” optical system        provides a system with a predetermined x-ray “bandwidth”.

The “high-energy” cutoff is well defined for a given material with acritical angle, and the attenuation of high energy x-rays preventsspurious signals from being observed at higher harmonics (e.g. twice(2×) the energy) downstream in the spectrometer. However, additionalstructure in the reflectivity spectrum may be observed at high energywith some materials. For some x-ray reflective optics, the reflectivitymay be designed to be below 25% for all energies greater than 1.2 timesthe cutoff energy. For some x-ray reflective optics, the reflectivitymay be designed to be below 10% for all energies greater than 1.2 timesthe cutoff energy.

3. Structured X-Ray Source.

The x-ray bandwidth for a given x-ray source target material andcombination of window/filter and x-ray optical system may or may notprovide the full range of x-ray energies needed for the measurement ofthe x-ray absorption spectrum of a given object to be examined.Achieving enough x-ray brightness in the spectral region of interest maybe an issue, and therefore, x-ray sources includes targets having x-raygenerating materials embedded into a thermally conductive substrate.X-ray source material could include one of several types of sources,including a solid continuous target or a micro-structured target.

Microstructured targets, x-ray generating materials, x-ray targetmaterials, microstructures of different shapes, and microstructures ofvarious materials such as those that may be used in embodiments of thepresent technology disclosed herein are described in US patentapplication entitled “STRUCTURED TARGETS FOR X-RAY GENERATION” (U.S.patent application Ser. No. 14/465,816, filed Aug. 21, 2014), thedisclosure of which is hereby incorporated by reference in its entiretyalong with any provisional applications to which said patent applicationclaims benefit.

Although the targets may be aligned to radiate x-rays using azero-degree take-off angle, as discussed above, some embodiments may usenear-zero degree take off angles using source configurations aspresented in, for example, U.S. patent application Ser. No. 15/166,274,filed May 27, 2016 by the inventors of the present application andentitled “DIVERGING X-RAY SOURCES USING LINEAR ACCUMULATION,” which ishereby incorporated by reference into the present application in itsentirety.

FIG. 3 illustrates a portion of a target comprising three x-raygenerating structures, each having a different x-ray generatingmaterial. By translating the target along the width direction so thatthe electrons 111 now bombard this second set of microstructures, asecond set of x-rays 1888 are produced. If the materials of the firstset 710 and second set 720 are distinct, the corresponding x-rays 1788and 1888 generated when selected for bombardment by electrons will alsohave distinct spectral properties.

Various targets include different x-ray generating materials may be usedin various embodiments. As illustrated in FIG. 3, multiple solidstructures 740, 750 and 760 of different x-ray generating materials maybe used in an anode target as well, with selection between targetmaterials made by translation of the target under the electron beam 111to select, for example, the third material 760, generating thecorresponding x-rays 1688.

Although the physical translation of the target under the electron beammay allow the materials to be “switched” from one to another whileproducing a beam that remains aligned with a single set of x-ray optics,other embodiments in which the electron beam is simply directed from oneset of materials to another may also be used. This may be beneficial incases where the different x-ray generating materials are aligned withdifferent sets of x-ray optics, with each set of optics tuned to matchthe radiation spectrum of x-rays for each material. Directing theelectron beam from one to the other therefore allows rapid switchingbetween spectral sources.

4. X-Ray Optical System.

Once x-rays are generated by a high-brightness x-ray source, a portionof the x-rays can be collected by an optical system to be subsequentlycollimated and/or focused onto the object to measure the x-rayabsorption and transmission.

Optical systems used in embodiments of the invention disclosed hereinhave been described in detail in the US patent application entitled“X-RAY ILLUMINATORS WITH HIGH FLUX AND HIGH FLUX DENSITY” (U.S. patentapplication Ser. No. 15/431,786, filed Feb. 14, 2017) and its parentapplications (U.S. patent application Ser. No. 15/269,855, filed Sep.16, 2016, and now issued as U.S. Pat. No. 9,570,265, and Ser. No.14/544,191, filed Dec. 5, 2014 and now issued as U.S. Pat. No.9,449,781), which are all hereby incorporated by reference in theirentirety, along with the provisional applications to which they claimbenefit.

Referring to FIG. 1, the generated x-rays will diverge from the x-raysource 80, and after passing from the source through an x-raytransparent window 40, an optical system 3000 includes a set of one ormore x-ray optical elements will intersect a portion of the x-rays andredirect their path of propagation.

The optical system 3000 may be a simple, single x-ray reflecting opticalelement with the topology of a hollow tube, or a more complex set ofx-ray optics. This optical system 3000 can be mounted along the axis ofbrightest illumination so that a portion of the diverging x-rays 888will reflect off the inner surface of the various optical elements. Thecurvature of the inner and/or inner and outer surface may take a numberof geometric forms, but a very useful set of geometric forms for anumber of optical elements are found among the quadric surfaces, and inparticular, spheroids, ellipsoids, paraboloids, hyperboloids, ellipticcylinders, circular cylinders, elliptic cones, and circular cones. Insome instances, at least a portion of a reflective surface of thereflective x-ray focusing optic is axially symmetric. In someembodiments, the reflective surface may be coated with a materialselected for its x-ray reflective properties, including its criticalangle. Such materials may include chromium, copper, rhodium, palladium,gold, silver, nickel, iridium, and platinum, among others.

These optical elements will typically be mounted such that a portion ofthe x-rays experience total external reflection from the inner surface,as was described above. The reflected x-rays from an individual opticalelement may be focused to a point or a line, or collimated, orconfigured to produce some other diverging or converging wavefront, butfor the embodiments presented here, the optical system produces aconverging wavefront of x-rays 887 that comes to a focus at an aperture272.

By placing an object 240 to be examined where it will be illuminated bythe converging x-rays 887, a transmitted diverging x-ray wavefront 888-Tis produced on the far side of the aperture 272, and may be subsequentlyanalyzed by the spectrometer.

4.1. Optics Configurations

Optical configurations for use with the present technology can beconfigured as an ellipse, parabola, paraboloidal, or other shape. FIGS.4A-5B illustrate exemplary optical reflectors.

FIG. 4A illustrates in cross section a possible optical configurationfor the optical system using the form of an ellipse. An ellipse has twofoci F₁ and F₂ such that any photons radiating from one of the foci willbe reflected and converge onto the other. By configuring the innersurface of a tube-shaped optical element 3010 to have an ellipsoidalsurface, and choosing the coating for the reflecting portion of the tubesuch that the angle of incidence for x-rays within a designatedbandwidth emerging from the x-ray source is smaller than the criticalangle, total external reflection is achieved. Then, at least a portionof the x-rays generated by an x-ray source placed at one of the fociwill be focused to the other focus.

FIGS. 4A and 4B illustrate a portion of an embodiment of the inventionutilizing such an ellipsoidal reflector 3010. An x-ray source includesx-ray generating microstructures 1700 embedded in a substrate 1000generate x-rays 888 when bombarded by electrons 111 in a vacuum. Thediverging x-rays 888 pass through a window 40 and enter the ellipsoidaloptical element 3010. A portion of the x-rays experience total externalreflection from the inner elliptical surface of a tube-like opticalelement 3010, and become focused x-rays 887 that converge onto anaperture 272 in an aperture component 270 after passing through theobject 240 to be examined. In some embodiments, the on-axis x-rays maybe blocked with a beam stop 1850. In some embodiments, as illustrated inFIG. 4A and the corresponding perspective view of FIG. 4B, the on-axisx-rays may be blocked with a beam stop 1850.

FIGS. 5A and 5B illustrate a portion of an embodiment of the inventionutilizing a paraboloidal reflector 3020. An x-ray source includes x-raygenerating microstructures 1700 embedded in a substrate 1000 generatex-rays 888 by linear accumulation when bombarded by electrons 111 in avacuum. A parabola has single focus F_(p) such that any photons radiatedfrom the point of focus will be reflected to form a parallel(collimated) beam. The diverging x-rays 888 pass through a window 40 andenter the first paraboloidal optical element 3020. A portion of thex-rays experience total external reflection from the inner paraboloidalsurface of the tube-like optical element 3020, and become collimatedx-rays 889.

Once collimated, a second optical element 3022 with a tube-shapedtopology and paraboloidal inner surface, as shown in FIGS. 5A and 5B,may be aligned with the optical axis of the first optical element 3020so that the collimated x-rays 889 are incident on the inner surface ofthe second optical element 3022 at angles smaller than the criticalangle for the surface. The reflected x-rays then become focused x-rays887 that converge onto an aperture 272 after passing through the object240 to be examined.

Although the illustration shows a second paraboloidal optical element3022 of the same size and shape as the initial paraboloidal opticalelement 3020, these need not be the same dimensions, but may haveparaboloid surfaces with different curvature and relative focuspositions.

In some embodiments, as illustrated in FIG. 5A and the correspondingperspective view of FIG. 5B, the on-axis x-rays may be blocked with abeam stop 1852. Although shown positioned between the two paraboloidaloptical elements, the beam stop may be at the entrance to the firstoptical element 3020, or at the exit of the second optical element 3022as well.

4.3. Other X-Ray Optics.

Other x-ray optical systems, such as Wolter Type I optics, cone shapedcapillary optics, Kirkpatrick-Baez optics, etc. may be used ascomponents of the optical system. Systems including filters andadditional beam stops, etc. may also be used.

The optical elements described above may be fabricated of any number ofoptical materials, including glass, silica, quartz, BK7, silicon (Si),Ultra-low expansion glass (ULE™), Zerodur™ or other materials.

The reflective coatings used for the various optical elements used inembodiments of the invention as described above may be of a singleelemental material, to take advantage of the total external reflectionfor angles of incidence smaller than the critical angle, and preferablymay be of higher mass density material (greater than 2.5 g/cm³) at least25 nm thick. Materials such as gold (Au), silver (Ag), platinum (Pt),etc. may be used as single-material coatings for these optical elements.

The reflective coatings may also be multilayer coatings, withalternating periodic layers of two or more materials, that provideconstructive interference in reflection for certain x-ray wavelengths.The reflection efficiency depends on the wavelength and angle ofincidence of the x-rays as well as the thickness of the alternatinglayers and number of layers, so this has limited use as a broadbandreflector, but may be used if specific wavelengths are desired. Amultilayer could also be depth graded and so the energy bandwidth couldbe “reasonably large.” such as for example 20-25% bandwidth has alreadybeen demonstrated for hard x-rays.

Combinations that may be used for multilayer reflectors may betungsten/carbon (W/C), tungsten/silicon (W/Si), tungsten/tungstensilicide (W/WSi₂), molybdenum/silicon (Mo/Si), nickel/carbon (Ni/C),chromiun/scandium (Cr/Sc), lanthanum/boron carbide (La/B₄C),tungsten/boron carbide (W/B₄C), and tantalum/silicon (Ta/Si),nickel/boron carbide (Ni//B₄C), and aluminum/alumina (Al/Al₂O₃), amongothers. The surface may also be a compound coating that includes analloy or mixture of several materials.

Other optical elements, such as Fresnel Zone Plates, cylindrical Wolteroptics, Wolter Type II optics, Kirkpatrick-Baez mirrors, Wolter Type IIIoptics, Montel optics, diffraction gratings, crystal mirrors using Braggdiffraction, hole-array lenses, multi-prism or “alligator” lenses,rolled x-ray prism lenses, “lobster eye” optics, micro channel plateoptics, or other x-ray optical elements may be used or combined withthose already described to form compound optical systems for embodimentsof the invention that direct x-rays in specific ways that will be knownto those skilled in the art.

5.0 Basic Spectrometer.

FIGS. 6-9 illustrate schematic cross-section views and a perspectiveview the elements of a spectrometer system that may be used in someembodiments of the invention. Turning to FIG. 6, the x-ray target 1100includes a substrate 1000 and x-ray generating material 1700 bombardedby electrons 111 in a vacuum. As drawn, the x-rays 888 emerge at anon-zero take-off angle relative to the surface, but other alignmentsusing a zero-degree take-off angle may be used as well.

The x-rays 888 that diverge from the x-ray source pass through thewindow 40 in the vacuum chamber, and are collected by an optical system.In the example of FIGS. 6-9, the optical system includes a singleellipsoidal capillary optic 3010 and a beam stop 1854. This single optic3010 has an inner surface that reflects x-rays at near-grazing anglesand focuses them onto the aperture 272 in the aperture component 270. Anobject 240 to be examined is positioned before the aperture component270, and the x-rays passing through the aperture 272 are those that havebeen transmitted through the object 240.

The aperture 272 will typically be a small hole of a diameter comparableto the size of the focused spot produced by the x-ray optical system.Aperture diameters of 5 to 25 microns may be typical in some embodimentsof the invention. In some embodiments of the invention, the aperture mayinclude a slit, in some instances generally oriented horizontally. Thesize of the aperture will generally be designed to correspond to theexpected size and dimensions of the focused x-ray beam. The aperturecomponent itself may include a piece of metal (e.g. molybdenum orplatinum) having a thickness shorter than the depth of focus for theoptical system (e.g. on the order of 20 microns thick).

On the far side of the aperture component 270, the x-rays emerge fromthe focus and are again diverging x-rays 888-T. The geometry willgenerally be an annulus of x-rays, as defined by the exemplary x-rayoptic 3010. As shown, the aperture 272 serves as the point of origin forthe x-rays entering the spectrometer 3700. Additional aperture(s) mayalso be used within the spectrometer to further block scattered x-rays.

In the spectrometer, the cone of x-rays 888-T will fall onto the surfaceof a diffracting crystal analyzer 3710, which will diffract x-rays ofdifferent wavelengths λ₁, λ₂, λ₃ λ₄, etc. (shown as ray bundles 887-A,887-B, 887-C, and 887-D etc., respectively) to different points on anarray detector 290. As shown in FIG. 5 and, in more detail in FIG. 6,the crystal analyzer will act as a Bragg diffraction element, reflectingthe x-rays if the correct conditions of wavelength and angle ofincidence are met. X-rays that are not diffracted 899 are typicallytransmitted through the crystal analyzer, and may be absorbed by a beamstop (not shown) or by the crystal, or by the crystal's mount.

In some instances, multiple crystals can be used in the x-rayspectrometer. When more than one crystal is used, each of the crystalsmay be selected based on monochromaticity requirements.

The crystal analyzer 3700 may be positioned ˜250 mm away from theaperture 272, and will typically have a width of about 1 cm. and alength smaller than 5 cm., but other dimensions may be used. The crystalanalyzer 3700 may include a single planar Bragg crystal, but inpractice, the crystal analyzer may be a thin crystal curved in thesagittal direction. This allows the x-rays diverging in the directionsperpendicular to the direction of propagation to be collected andfocused onto the detector 290, while allowing the x-rays to bediffracted by wavelength along the direction of propagation. For someembodiments, a bending radius between 50 and 200 mm may be used. Suchconfigurations are sometimes called a von Hamos Spectrometer.

Curved crystal analyzers such as those made from thin wafers of singlecrystal silicon with (111) and (220) planes parallel to the surface maybe used in some embodiments of the invention. Single crystal siliconanalyzers may be grown onto a curved substrate or bent and glued to asimilarly shaped substrate.

In some instances, crystal analyzers can include graphite, highlyoriented pyrolytic graphite (HOPG), or highly annealed pyrolyticgraphite (HAPG). These embodiments may be produced by growing a graphitelayer (e.g., 5 and 200 microns thick) onto a curved substrate.

FIGS. 8A and 8B illustrate a spectrometer 3730 using a crystal analyzerin the form of a mosaic crystal 3733. In the mosaic crystal 3733, thecrystal analyzer includes an ensemble of micro-crystals at varied anglesthroughout the material, each as small as a few hundred nanometers or aslarge as several microns, held with a backing 3734, typically made ofmetal. Transmitted x-rays that were not diffracted by the micro-crystalat the surface may still be diffracted from another micro-crystalpositioned deeper within the mosaic.

Although the entire spectrum of x-rays transmitted through the object240 will be present at all points of the transmitted annulus of x-rays888-T, dispersion is achieved because the diverging cone has a varietyof angles of incidence on the crystal analyzer, and therefore for atleast some angle of incidence, x-rays of a particular energy within thedesignated x-ray bandwidth may be reflected. However, all otherwavelengths at the same angle of incidence will not be diffracted, andwill be partially or completely absorbed by the crystal analyzer shownas transmitted x-rays 899 in FIGS. 5 and 6).

FIG. 8B illustrates the relationship for which additional collection ofx-rays may occur. The origin (the aperture in this case), thediffracting crystal, and the point of convergence at the detector allfall along the Rowland Circles 808-A and 808-D for the correspondingwavelengths. Although other micro-crystals are present in the mosaiccrystal, only those that lie along the Rowland Circle and have thecorrect orientation will diffract x-rays to converge to the sameposition at the detector 290. X-rays of varying wavelengths distributedthroughout the diverging beam 888-T have a better chance of encounteringa properly positioned and oriented micro-crystal, increasing the numberof x-rays directed towards the detector. Use of mosaic crystals cancollect as much as 30 times the amount of x-rays that a single crystaldiffraction element can produce.

FIG. 8B includes the elements of FIG. 8A, but additionally shows theRowland Circles 808-A and 808-D for the two x-ray wavelengths, and alsoonly illustrates representative micro-crystals on the mosaic crystalcontributing to the diffraction for the two wavelengths. Althoughmicro-crystals with “random” orientations are illustrated in FIG. 8A todramatically illustrate the mosaic non-uniformity, most mosaic crystalswill be more closely aligned with the Bragg angles at the angles ofincidence for which they are designed.

FIG. 9 illustrates a schematic perspective view of a system using acurved crystal analyzer having a mosaic crystal that distributes thespectrum along one axis, while focusing x-rays in the other (sagittal)axis. As noted before, it should be clear that the drawings presentedhere are not illustrated to scale, but have been created to better pointout how the invention is to be made and used.

For more on crystal or multilayer reflectors, see James H. Underwood,“Multilayers and Crystals”, Section 4.1 of the X-ray Data Booklet, whichmay be downloaded at: xdb.lbl.gov/Section4/Sec_4-1.pdf, and which ishereby incorporated by reference.

5.2. Detectors.

The detector 290 typically includes a 2-D pixel array 294, in which oneaxis is significantly longer than the other. A 2048×256 pixel array maybe typically used, although a detector with at least 128 pixels alongthe long axis (the dispersive direction) may be preferred. For someconfigurations where the beam cross sections are smaller and thedistances are shorter, fewer pixels may be used. Also, if a portion ofthe beam is to be blocked, fewer pixels may be used. The long axis willbe aligned along the direction of x-ray propagation, and the dispersionof x-rays by wavelength will occur along that axis. The short axis willbe aligned with the sagittal direction. The diffracted x-rays may notform a perfect spot, and so detection using multiple pixels may providea higher collection efficiency.

The detector may be any one of a number of x-ray array detectors, suchas a CCD array, a CMOS or S-CMOS detector, a flat panel sensor, or anyone or more position sensitive x-ray array detectors known in the artthat converts x-ray intensity to an electronic signal, including 1-Dline and 2-D array detectors. Such examples of position-sensitivedetectors include linear detectors, position-sensitive array detectors,pin diodes, proportional counters, spectrometers, photodiode detectors,scintillator-type and gas-filled array detectors, etc.

Energy resolving pixel array detectors may also be used. In thesedetectors, each pixel also provides information on the energy of x-raysdetected, and may be especially useful when the object producessignificant fluorescence. Also known as energy resolving x-rayspectrometer, such a detector uses a semiconductor device to measure theenergy of the detected x-ray photons. The silicon PIN photodiode(Si-PIN) is a simple and low cost class of EDS spectrometer thattypically has the lowest performance in terms of energy resolution.Energy resolving pixel array spectrometers are available and may be usedin some embodiments of the invention.

Another type of detector, known as a pixel array microcalorimeterspectrometer, uses typically a superconductor circuit to measure changeof the electric response from absorption of an x-ray photon.

In some instances, the spectrometer may include a mechanism, such as ashielding component, that prevents undesired x-rays from being detected.For example, at least one x-ray shielding component can be implementedthat prevents x-rays not-dispersed by the wavelength dispersivecomponent from arriving at the detector.

Additional configurations may involve additional filters (e.g. thinfoils containing the appropriate element(s)) along the beam path beforethe detector to preferentially attenuate some unwanted x-rays fromarriving at the spectrometer, reducing the background due to thedetection of the x-rays scattered from the object or reduce total x-rayflux entering the spectrometer to avoid saturation. Multiplespectrometers of the same type or combination of two or more types canbe used simultaneously or interchangeable to utilize their respectivestrength individually or collectively.

Other detector geometries and arrangements may be known to those skilledin the art. For more on x-ray detectors, see Albert C. Thompson, “X-RayDetectors”, Section 4.5 of the X-ray Data Booklet, which may bedownloaded at: xdb.lbl.gov/Section4/Sec_4-5.pdf which is also herebyincorporated by reference.

5.3. Options and Versatility.

As discussed above, a single x-ray generating material combined with aselected coating for an x-ray optic may provide a limited bandwidth foran x-ray optical system that avoids unwanted characteristic lines andprovides a particular region of an absorption spectrum for an object tobe investigated. However, any given x-ray generating material with anygiven optical coating will generally not provide the full spectral rangeneeded to characterize an object in transmission.

FIG. 10 provides a schematic illustration of a spectrometer systemhaving a diversity of options built into the system. The target 1102includes a substrate 1002 and two (or more) different types of x-raygenerating materials 1702 and 1704. The mount 34 upon which the targetis secured not only connects to the electrical lead 32, but also has acontroller 36 that allows physical motion in a lateral direction for theselection of the material to be bombarded by electrons 111.

The system of FIG. 10 also has three different optical systems 3010-A,3010-B and 3010-C supported in a mount 3016 that allows the set ofoptical systems to be moved laterally to allow alignment of any of theoptical systems (which may use different material coatings and filtersinside to allow different x-ray bandwidths) with any of the x-raygenerating targets 1702, 1704 etc. As illustrated, the rightmost x-raygenerating material 1704 is being bombarded by electrons, and the leftmost optical system 3010-A is positioned to collect the x-raystransmitted through the window 40.

As before, the converging x-rays 887 emerging from the optical systemare focused onto an aperture 272 in an aperture component 270, and alsopass through the object 240 to be investigated. The resulting x-raysdiverging from the aperture 272 become the “virtual origin” for thex-rays diffracted by the spectrometer 3700.

However, the aperture component 270 may have multiple openings, such ascircular apertures 272 and 274 having different sizes, or slits 275 and277 of different sizes.

As before, the spectrometer 3731 includes a mosaic crystal analyzer 3733that disperses the x-rays onto the x-ray sensor 294 of the detector 290.However, in case the wavelength range is insufficient to span the entirespectrum in a single shot, this spectrometer 3731 also includes a mount3740 that allows the crystal analyzer 3710, an x-ray wavelengthdispersive element, to rotate about an axis perpendicular to thedirection of x-ray propagation. This allows a larger range of x-raydispersion to be measured using a single detector.

Such a multi-source/multi optic system may be used to collect x-rayspectra in a sequence of bands. For example, a first measurement may betaken using a source/optic combination to provide an x-ray spectrumbetween 4 and 5 keV; the next a different combination to provide aspectrum between 5 and 6 keV; and the next a third combination toprovide a spectrum between 6 and 7 keV, etc. Rotation of the crystalabout the axis may expand the range of energies collected from the samesource/optic combination.

In other variations, optical systems with a variety of beam stops may beused. Beam stops may be positioned at the entrance to the opticalsystem, at the exit of the optical elements of the optical system, or inbetween elements of the optical system. In some embodiments with asingle condenser optic, there may be a stop on both the entrance sideand the exit side of the condenser optic, with the exit-side stop being˜⅔ the size of the entrance stop. These stops will both block thethrough-beam, and in addition, the exit stop will also block a goodportion of any scattered x-rays from the condenser optic. This providesfor a cleanly reflected x-ray beam.

In other variations, a number of shielding elements may be used to blockor reduce unwanted x-rays from being detected. Scattering and x-rayfluorescence may occur every time x-rays encounter a component of thesystem. Likewise, x-rays not diffracted by the crystal analyzer will betransmitted through the analyzer, and may create additional scatteredand/or fluorescence x-rays unless a suitable beam absorbing element ispositioned behind the analyzer. Although these unwanted x-rays will notpropagate along the principle beam-path of the system in the way thatthe focused x-rays propagate, they may still find their way through thesystem and onto a detector element unless additional shielding isinstalled.

In other variations, the entire system (and not just the x-ray source)may be enclosed in a vacuum chamber, removing the need for the window 40be present to maintain the vacuum around the x-ray source. Likewise, theoptical system and spectrometer may be flushed with helium gas, toreduce scattering in the system.

5.4. X-Ray Emission Spectroscopy (XES).

Another embodiment adapted to detect the spectrum of x-ray fluorescencefor use in x-ray emission spectroscopy (XES) is shown in FIG. 11. Theembodiment of FIG. 11 is similar to the configuration illustrated inFIG. 6, except the object 240-F emits x-ray fluorescence 877. Thisfluorescence will generally be emitted in all directions from the object240-F. Therefore, to block the x-rays 888-T directly transmitted throughthe object 240-F, a beam stop 254 is positioned after the aperturecomponent 270, and only the x-ray fluorescence 877 emerging from theobject 240-F around the beam stop 254 propagates onward to the crystalanalyzer 3710. The crystal analyzer 3710 then disperses the fluorescenceaccording to wavelength, with x-rays 877-A, 877-B, 877-C, 877-D, etc. ofdifferent wavelengths directed to different positions on the detectorsensor 294.

6.0 Methods of Spectroscopic Data Gathering.

The process steps to measure the transmission spectrum of an objectaccording to an embodiment are represented in FIGS. 12A, 12B, and 12C,and are described below.

In the first step 4610 an object to be examined is selected, and thex-ray spectral range over which transmission information is desired isselected. The object may be any type of object, as long as a significantnumber of detectable x-rays are transmitted through the object.

In the next step 4620, an x-ray target that will produce x-rays in thespectral range when bombarded by electrons is selected. This may includea target with any number of x-ray generating materials that have beenmentioned in the patent applications cited above, including tungsten,molybdenum, copper, rhodium, etc. The target may include a single x-raygenerating material, or multiple x-ray generating materials, and mayfunction in the x-ray source as a static or as a rotating anode.

In the next step 4630, a reflective x-ray focusing optic or opticalsystem is selected that has a particular high-energy cutoff. This mayarise from the material of the optic itself, reflective coating thathave been applied to the optic or optical elements, or filters that area part of the optical system.

The focusing optic will be designed to collect x-rays and focus them toa particular focal plane, and so in the next step 4640, the position inspace where this focus plane will occur will be determined. This may beset by simply placing the optic into a predetermined position, or mayrequire some alignment and adjustment of the position of the optic andthe target within x-ray source, as noted in step 4660. Before this stepis carried out, however, a decision step 4644 occurs, in which adecision is made as to whether an aperture or slit in the focal planeshould be used. If the decision is yes, then a step 4650 in which theaperture or slit is positioned in the focal plane is carried out beforethe subsequent alignment step 4660.

Once the position of the x-rays in the focal plane (or the location ofthe aperture/slit) has been determined, the crystal analyzer is alignedto collect x-rays emerging from the focal plane (or aperture/slit, ifused) and disperse them. The crystal analyzer may be any analyzer asdescribed previously, including a single crystal structure, a mosaiccrystal, etc.

In the next step 4680, the x-ray detector, generally a 2-D arraydetector as described above, will be placed to detect the x-raysdispersed by the crystal analyzer. This step will typically complete thealignment phase of the method, and the method proceeds to the stepsshown in FIG. 12B, with the handoff designated by the circled X in thefigures.

Referring now to FIG. 12B, in the next step 4810, the electrons bombardthe target and x-rays are generated.

In the next step 4820, the transmission x-ray spectrum of the instrument(without the object in the optical path) is recorded. This serves as thereference data against which the subsequent measurements will be made.

In the following steps, the object will be positioned to be illuminatedby x-rays. A decision 4822 to use or not use a shutter to block the beammade, and, if positive, the shutter is used to block the beam in step4830, and in the next step 4840 the object may be positioned without thex-rays illuminating the object. Once positioned, the next step 4850unblocks the x-ray beam, allowing the object to be illuminated by thex-rays. If the shutter is not used, then in step 4844 the object may bepositioned while the x-rays beam is still on.

Once the x-rays illuminate the object, in the next step 4860 the x-raystransmitted through the object and then dispersed by the spectrometerare detected by the detector sensor and recorded.

Now that an x-ray transmission for the system with and without theobject have been recorded, in the next step 4870 the two results may becompared, and the results of the comparison may be used to calculate thetransmission spectrum of the object in the following step 4880. From thetransmission results, the absorption spectrum of the object may also beinferred.

The transmission spectrum so generated represents the spectrum of theobject at a single point of illumination in the object for a singlex-ray bandwidth range (selected by the choice of optic and target in theprevious steps). The method then proceeds to the next steps, representedby the circled Y in the FIGS. 12B and 12C, in which alternativevariations of the data may be collected.

In the next step 4882, it is determined whether information aboutadditional points in the object need be collected; i.e. is there a“scan” of the object desired that forms a “map” of the spectralproperties of the object. If so, the new position coordinates for theobject are provided in the next step 4885, and the path of controlproceeds to the position marked with a circled B in FIG. 12C and back toFIG. 12B, where the process of steps 4822 4844, 4830, 4840, 4850, 4860,4870, 4880 and 4882 are repeated in a loop until the entire desiredareal dataset for the object has been completed.

If the dataset is complete, the next step 4888 determined whether thedata collected will be a 2-D dataset (representing, for example, aplanar “map” of the object) or if a 3-D representation of the object foranalysis, using algorithms related to, for example, laminography ortomography, may be required. If 3-D data for this energy range isdesired, the process determined in the next step 4892 whether in factthe 3-D data collection is complete. If not, the settings for adifferent relative rotational orientation for the object relative to thex-rays are determined in the next step 4895, and control proceeds to theposition marked with a circled B in FIG. 12C and back to FIG. 12B, wherethe process of steps 4822 4844, 4830, 4840, 4850, 4860, 4870, 4880,4882, 4885, 4888, 4892, and 4895 are repeated in a loop until the entiredesired 3-D dataset for the object has been completed.

Once the 2-D and/or 3-D data collection has been completed, in the nextstep 4900 it is determined whether additional information for adifferent x-ray spectral range is required. If the collected dataset isadequate, the process ends. Data collection is complete.

If, on the other hand, additional spectral data is required, in the nextstep 4950 a new spectral range is determined, and control passes throughthe path marked with the circled A in FIG. 12C and back to FIG. 12A,where the process beginning with step 4620 repeats using the newspectral range.

Variations on the method described above may also be put into practice.For example, instead of first executing a loop of data collection in x-and y-dimensions at a fixed rotation position, and then changing therotation setting to collect additional data, embodiments in which theobject is rotated while the x- and y-position settings remain fixed mayalso be executed. Rotation of the object around the z-axis may alsoprovide additional information that can be used in image tomosynthesis.Likewise, data for various spectral ranges may be collected with orwithout the completion of 2-D or 3-D scans.

7. Limitations and Extensions.

With this application, several embodiments of the invention, includingthe best mode contemplated by the inventors, have been disclosed. Itwill be recognized that, while specific embodiments may be presented,elements discussed in detail only for some embodiments may also beapplied to others. Also, details and various elements described as beingin the prior art may also be applied to various embodiments of theinvention.

While specific materials, designs, configurations and fabrication stepshave been set forth to describe this invention and the preferredembodiments, such descriptions are not intended to be limiting.Modifications and changes may be apparent to those skilled in the art,and it is intended that this invention be limited only by the scope ofthe appended claims.

Elements as shown in the drawings are meant to illustrate thefunctioning of various embodiments of the invention, and should not beassumed to have been drawn in proportion or to scale. Likewise, anysingle figure should not be construed as being an illustration showingall elements of any particular embodiment of the invention.

1.-22. (canceled)
 23. An x-ray spectrometry system comprising: an x-raysource configured to generate x-rays having a first spectrum; an x-rayoptical system configured to receive, focus, and spectrally filter thex-rays to form an x-ray beam having a second spectrum that isattenuated, as compared to the first spectrum, in an energy range abovea predetermined energy, the x-ray beam having a focus at a predeterminedfocal plane; a mount configured to hold a sample in a path of the x-raybeam from the x-ray optical system; and a x-ray spectrometer thatreceives at least some of the x-rays from the sample and analyzes thereceived x-rays.
 24. The system of claim 23, further comprising anaperture in the path of the x-ray beam, the aperture configured to allowthe at least some of the x-rays from the sample to pass through theaperture to the x-ray spectrometer.
 25. The system of claim 24, whereinthe aperture is at the focal plane.
 26. The system of claim 24, whereinthe aperture has a width in a range of 5 microns to 25 microns.
 27. Thesystem of claim 23, wherein the at least some of the x-rays from thesample comprise x-rays generated by fluorescence within the sample. 28.The system of claim 23, wherein the at least some of the x-rays from thesample comprise x-rays of the x-ray beam that are transmitted throughthe sample.
 29. The system of claim 23, wherein the x-ray optical systemcomprises at least one reflective x-ray focusing optic.
 30. The systemof claim 29, wherein at least a portion of a reflective surface of theat least one reflective x-ray focusing optic is axially symmetric. 31.The system claim 29, wherein at least a portion of a reflective surfaceof the at least one reflective x-ray focusing optic has a quadricprofile.
 32. The system of claim 23, further comprising a beam stopconfigured to block a portion of the x-rays that are not focused by thex-ray optical system from impinging the sample.
 33. The system of claim23, wherein the x-ray spectrometer comprises a wavelength dispersiveelement and an array detector configured to receive x-rays dispersed bythe wavelength dispersive element.
 34. The system of claim 33, whereinthe x-ray spectrometer further comprises at least one x-ray shieldingcomponent configured to prevent x-rays that are not dispersed by thewavelength dispersive element from arriving at the array detector. 35.The system of claim 33, wherein the wavelength dispersive elementcomprises at least one crystal analyzer.
 36. The system of claim 35,wherein the at least one crystal analyzer comprises a mosaic crystal ora plurality of crystals, each crystal of the plurality of crystalshaving a corresponding monochromaticity.
 37. The system of claim 33,wherein the x-ray spectrometer comprises a mechanism to rotate thewavelength dispersive element.
 38. The system of claim 23, wherein thex-ray spectrometer is a Rowland circle geometry spectrometer.
 39. Thesystem of claim 23, wherein the x-ray spectrometer is a von Hamosspectrometer.
 40. A method for x-ray spectroscopy, the methodcomprising: receiving x-rays having a first spectrum; focusing andspectrally filtering the received x-rays to form an x-ray beam having asecond spectrum, the second spectrum attenuated, as compared to thefirst spectrum, in an energy range above a predetermined energy, thex-ray beam having a focus at a predetermined focal plane; irradiating asample with at least some of the x-rays of the x-ray beam; and using awavelength dispersive element to analyze x-rays from the sample.
 41. Themethod of claim 40, wherein the x-rays from the sample comprise x-raysgenerated by fluorescence within the sample.
 42. The method of claim 40,wherein the x-rays from the sample comprise x-rays of the x-ray beamthat are transmitted through the sample.
 43. The method of claim 40,wherein the x-rays from the sample are transmitted through an apertureat the focal plane.
 44. The method of claim 40, wherein said focusingand spectrally filtering comprises reflecting the x-rays from at leastone reflective x-ray focusing optic.
 45. The method of claim 44, whereinthe at least one reflective x-ray focusing optic has an x-rayreflectivity less than 25% for x-rays with energies above 1.2 times apredetermined cutoff energy.
 46. The method of claim 40, wherein saidusing the wavelength dispersive element comprises dispersing at leastsome of the x-rays from the sample as a function of x-ray wavelength andanalyzing a spectral distribution of at least some of the dispersedx-rays.
 47. The method of claim 46, wherein said analyzing the spectraldistribution comprises recording an intensity of the at least some ofthe dispersed x-rays as a function of position.